import java.lang.Thread;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.io.*;
import java.util.*;
import java.text.*;

public class LockedFile
{
	private ReentrantReadWriteLock theLock = new ReentrantReadWriteLock(true);

	private void testLocking()
	{
		theWriter w1 = new theWriter("A");
		new Thread(w1).start();
	}
	public static void main(String[] args)
	{
		LockedFile lv = new LockedFile();
		lv.testLocking();
	}
	private class theWriter implements Runnable
	{	private String name;
		public theWriter(String theName)
		{	name = theName;		}
		public void run()
		{
			try
			{
				theLock.writeLock().lock();
				// open file and write
				try
				{
					PrintWriter output = new PrintWriter("file.txt");
					Date dNow = new Date( );
      		SimpleDateFormat ft = new SimpleDateFormat ("HH:mm:ss SSS");
					output.println("The Writer " + name +
						" with the value "+ ft.format(dNow));
					output.close();
				} catch (java.io.FileNotFoundException e) {}
				try
				{
					Thread.sleep(2000);
				}
				catch (InterruptedException e)
				{}
			} finally
			{
				theLock.writeLock().unlock();
			}

		}
	}
}